In the event of arthrosis in joints between bones, and in particular in a metatarso-phalangeal joint, it is often necessary to perform arthrodesis in order to fuse the two bones together. As a general rule, arthrodesis constitutes an operation that is difficult in that it sets a joint in a position that is defined and it does so in a manner that is not reversible. Thus, it is very important for arthrodesis of a metatarso-phalangeal joint to be performed correctly insofar as the joint is involved as an essential actor in the walking cycle of a human being. It will thus be understood that it is essential for the two bones to be positioned relative to each other prior to fusion with an orientation that is implemented as accurately as possible in order to avoid any subsequent difficulty.
It is therefore essential for the axes of the bones to be fixed relative to each other so as to comply as well as possible with the flexing and the axes of the patient, and this must be done as a function of the patient's sex, gait, and morphology.
Until now, metatarso-phalangeal arthrodesis has been performed using fixing plates of a variety of shapes and provided with slots for receiving fixing screws in order to secure the plate to each of the two bones to be fused together.
Thus, by way of example, fixing plates are known that present a curved “quarter-tube” cross-section which the surgeon places across the joint between the bones to be fused together. That known plate is bent by the surgeon so as to take up an angle in the dorsi-flexion plane having a value that has been determined by the surgeon and that is specific to the patient. Once a joint has been blocked, plates of that type thus make it possible to confer a particular orientation in elevation on one of the two bones on which arthrodesis is performed. This constitutes an advantage to the patient since the joint is blocked under conditions close to normal conditions of use for that joint, thereby reducing difficulty for the patient while walking and reducing possible future complications. Nevertheless, fixing plates of that type turn out to suffer from a variety of drawbacks, and in particular they are quite difficult for the surgeon to bend. In addition, it turns out that bending is rarely performed with sufficient accuracy and that bending gives rise to deformed zones of the plate presenting edges that can be quite sharp and likely to generate irritation or inflammation on coming into contact with adjacent tissue such as tendons, muscles, ligaments, skin, etc. Finally, plates of that type are unsuitable for bending through a varus-valgus angle, which means that they are not capable of implementing arthrodeses that are sufficiently close to conditions of optimum geometrical orientation between the two bones to be fused together for the purpose of reducing to the greatest possible extent any risk of subsequent difficulties and complications for the patient.
Fixing plates that are completely plane are also known, and although they greatly reduce the risk of complications for the patient following the operation of installing them, insofar as no bending is performed, they nevertheless do not make it possible to perform an arthrodesis in which the bones present specific dorsi flexion and varus-valgus angles.
As a general rule, it also turns out that fixing plates for bending by the surgeon require a special bending tool to be used that is specific to each type of plate, thereby constituting a further constraint. Finally, it turns out that a fixing plate that has been bent suffers from weakening of its metal in the bend zone, and that can constitute a drawback in terms of strength. Furthermore, the need to provide openings through the plate for passing fixing screws complicates the operation of bending the plate, specifically because of the presence of said openings.